This invention relates, in general, to semiconductor packages, and more particularly to a semiconductor package having recessed die cavity walls.
An often encountered problem in the assembly of semiconductor packages occurs when die attach material flows out of the die cavity and onto bond pads and bond posts. This problem greatly affects the wire bonding ability and reduces the attainable yield. Prior attempts to remedy this problem have been somewhat successful although they have not completely eliminated the problem and are often difficult to implement.
Prior art solutions include the formation of a moat within the die cavity. Excess die attach material flows into the moat before it flows up the cavity wall or the side of the semiconductor die. The use of this type mode has been successful in pressed ceramic packages as well as other one piece packages wherein the moat may be formed without significant variance in the fabrication process. However, moats are more difficult to form in laminated multilayer ceramic packages. The formation of a moat in this type package would most likely require use of an additional ceramic layer disposed so that desired package tolerances might be maintained. This would cause a significant increase in the difficulty and cost of manufacturing laminated multilayer ceramic packages.
Another prior art method of solving the die attach material overflow problem has been to enlarge the size of the die cavity. Although this helps with the die attach material overflow problem, there are many logistical problems that are incurred by enlarging the die cavity size. First, the enlarged die cavity requires additional space and therefore, a larger semiconductor package is needed to maintain the required internal dimensions of the package. Second, there will be a larger space between the semiconductor die and the bond posts which are disposed about the cavity thereby increasing the length of the bonding wires and jeopardizing reliability.
A further method of solving the die attach overflow problem is disclosed in copending application Ser. No. 07/286,676 entitled "Semiconductor Package Having an Outwardly Arced Die Cavity" filed on Dec. 19, 1988. This application discloses a semiconductor package wherein the die cavity includes a plurality of sides that are outwardly arced from the center of the die cavity. This configuration allows for reduced number of rejects due to die attach material overflow while reducing the minimum necessary die cavity size. Although this method has met a good deal of success, it is advantageous to have other methods of reducing die attachment material overflow problems. In view of the above, a die cavity that would reduce the die attachment material overflow problem while maintaining or reducing the minimum necessary cavity size would be highly desirable.